1. Field of the Invention
The present invention relates generally to a method forming a single-phase multi-element film constituted by at least four elements on a substrate by plasma-enhanced atomic layer deposition (PEALD).
2. Related Art
Copper wiring has been used for logic devices, and dielectric films have been applied for copper wiring, which films are deposited by chemical vapor deposition (CVD) or spin-on dielectric (SOD). For example, a Cu-cap film used as a diffusion blocking film for copper is constituted by a dielectric material such as SiN. As miniaturization of devices progresses, a dielectric film having a dielectric coefficient (k value) as low as 5 or less is required. However, for a layer structure formed by damascene methods, such a dielectric film need not have a good step coverage or conformality. However, depending on the type of layer structure formed by, e.g., deposition and etching, a dielectric film is required to have a good step coverage or conformality as well as a good resistance to chemicals, in addition to a low dielectric constant. It is difficult to deposit a dielectric film having the above properties by CVD.
From the above viewpoints, a dielectric film is deposited by atomic layer deposition (ALD) which is suitable for depositing a film having a good step coverage, particularly by plasma-enhanced ALD (PEALD), rather than thermal ALD, in consideration of potential damage caused to films due to heat. Further, since a two-element film such as SiN may not have sufficient etch selectivity and good dielectric constant, a multi-element dielectric film consisting of more than two elements is under development. However, it is not easy to deposit a high-quality multi-element dielectric film by ALD, since ALD using multiple elements involves problems such as interference with adsorption of one gas by adsorption of another gas.
Any discussion of problems and solutions in relation to the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made.